When couples make that lifetime commitment to each other in front of friends and family on one of the biggest days of their lives, few of them cite the 1,138 federal rights they will gain by making the promise of marriage. And the words "tax benefits" rarely come up in the best man's toast.

Yet "rights and benefits" are what the lesbian-gay-bisexual-transgender (LGBT) community has been using as its lead argument for decades. Recently, however, there's been a significant shift in the movement, one that is evident in the debate around marriage in Maryland. Rather than focusing on the legal rights and benefits of marriage — such as Social Security payments, spousal health care coverage and joint tax filing — many advocates have begun to emphasize the personal aspects of the marital bond, like commitment and responsibility. This paradigm shift was based on more than just savvy intuition; it's grounded in substantial public opinion research.

At Third Way, for example, we went beyond traditional polling and conducted a series of innovative and intensive one-on-one interviews — akin to the sort of market research tool used by the Fortune 500. Those interviews proved revelatory and have profound implications for extending marriage to lesbian and gay couples.

We started with a simple question: "What does marriage mean to you?" People spoke of the kinds of things you hear in a wedding ceremony: lifetime commitment, responsibility and fidelity. They called marriage "a big step" and "the most important decision of one's life." Nobody talked about legal rights or taxes.

Then we asked them why gay people might want to get married. The overwhelming answer? "I don't know." But when we probed deeper, we found that they did have some idea — they had heard the messages from LGBT advocates. They would talk about how gay couples want rights, benefits, equality and fairness. Not surprisingly, that led them to the idea of civil unions, because they told us that if you want legal rights, you should have a legal contract. But that (in their minds) had nothing to do with marriage.

To them, all the talk about rights indicated that gay couples "just don't get it" — that they couldn't really understand the true purpose of marriage. This feeling was reinforced by images many had seen of gay weddings held en masse, some during raucous gay pride parades. One research subject was particularly upset by a picture we showed of a lesbian couple getting married because the women were wearing jeans. He observed that he and his wife had taken six months to plan their wedding, and said: "To me, it looks like they called up the day before and said, 'Hey, do you want to go get married?'" Those interviewed saw a wedding as a joyful but weighty occasion, freighted with solemn, lifelong vows.

Once we identified this chasm between how Middle America understood marriage and what they heard from activists, we knew that if advocates wanted to make the leap from civil unions to marriage, they had to find a way to close that divide. Moderates needed to hear that gay couples understand that marriage is essentially about vows, not rights. And they needed to see that gay couples would take the tradition seriously and cherish — rather than mock, even inadvertently — the institution of marriage.

Many in the movement have now begun to make that shift. Freedom to Marry, a leading advocacy group, recently rolled out a public education campaign titled "Why Marriage Matters." Their focus isn't hospital visitation or tax savings; it's "Love. Commitment. Family." And locally, Equality Maryland's website describes marriage as "one of the few times where people make a public promise of love and responsibility for each other and ask our friends and family to hold us accountable."

Even in the context of litigation, the married gay couples who have filed federal constitutional challenges in Massachusetts have focused on the responsibilities that come with marriage. Immediately after a judge handed down a landmark legal decision saying Nancy Gill's constitutional rights had been violated, the lead plaintiff's victory statement reminded listeners that she and her wife "married out of love and commitment to each other first and foremost."

With the politics of relationship recognition for gay and lesbian couples evolving rapidly (witness the muted response of the GOP leadership to the Obama administration's refusal to defend the "Defense of Marriage Act"), advocates are poised to take some big steps forward. The sooner that we are able to replace the public's mental image of gay people demanding their rights with one of committed couples vowing to care for one another "for better or worse," the sooner they will be able to say "I do."

Lanae Erickson (lerickson@thirdway.org) is the deputy director of Third Way's Culture Initiative, and Jonathan Cowan is the president of Third Way, a moderate, progressive policy organization.